Constrain rotation

I know this question keeps coming up and I promise I've read the previous threads I could find on this. I have an actor that has self.rotation=0 and when touch is pressed rotate clockwise at speed 50. When you stop pressing on the actor, I have it interpolate self.rotation back to 0. So it basically swings clockwise, with self.rotation being either 360-->310 or 0-->-50. I want the player to only be able to swing the actor 50 degrees (to 310 or -50). But when I try to constrain with min/max, it doesn't work.